Cylinder papermaking machine containing a water impervious cylinder



United States Patent 3,397,112 CYLINDER PAPERMAKING MACHINE CONTAIi ING A WATER IMPERVIOUS CYLINDER Allan Peter Highton and John Brian Wheeldon, Kent, England, assignors, by mesne assignments, to Bowaters United Kingdom Paper Company Limited Filed Apr. 30, 1964, Ser. No. 363,952 Claims priority, application Great Britain, May 6, 1963, 17,794/ 63 5 Claims. (Cl. 162318) The present invention relates to a method of and apparatus for making a fibrous web such as paper in a continuous manner.

The Fourdrinier machine for making paper requires a considerable floor space because of the length of the Fourdrinier Web forming wire. Removal of water from the forming wire is by gravity, table roll suction, and suction boxes, which require a considerable amount of power and hence are comparatively expensive to operate. Although Fourdrinier paper making machines can be run at comparatively high speed, for example, 3,000 ft. per minute, this at the present time is about the maximum speed.

Machines for making paper and like fibrous web are known, in which the paper web is formed between a travelling Wire and the surface of a rotating cylinder. Such machines employ suction boxes for extracting Water, which boxes are mounted internally and/or externally on the rotating cylinder. In all known constructions of this particular type of machine, the formed web is carried away from the cylinder surface on the forming wire and then stripped therefrom.

The present invention relates to web forming apparatus particularly suited for the manufacture of paper in which the web is formed between the surface of a rotating cylinder and a travelling forming wire. The invention seeks to provide an improved construction of such apparatus which does not require the use of suction boxes for the extraction of water, which produces a web of a lower water content and hence stronger than has been possible with known machines and which permits a substanial saving in floor space.

According to the present invention a method of making a fibrous web, such as paper, in a continuous manner comprises depositing a fibrous stock in the nip between a surface of a rotating cylinder impervious to the liquid of the stock and a travelling liquid pervious band entrained around a portion of said cylindrical surface expelling sufficient stock liquid from the fibrous material whilst it is confined between the cylindrical surface and band, through said band to form a fibrous web adhering to the cylindrical surface, entraining the band away from the cylindrical surface, passing the fibrous web through the nip or nips of one or more felted press rollers bearing against the cylindrical surface, thereby further to dry the web and stripping it from the cylindrical surface.

Preferably the fibrous material is squeezed whilst it is confined between the cylindrical surface and the band, to expel stock liquid and form the fibrous web.

Preferably the web is dried to a suflicient extent so as to be self supporting before it is stripped from the cylindrical surface.

Also according to the present invention, apparatus for making a fibrous web such as paper, in a continuous manner comprises a cylinder having a liquid impervious surface, rotatable about a horizontal axis, an endless liquid pervious band entrained around a portion of the cylinder surface and movable therewith, one or more felted press rollers adapted to bear against the cylinder surface at a location or locations circumferentially spaced beyond, with respect to the direction of rotating "ice of the cylinder, the endless band, means adapted to deposit continuously fibrous stock between the band and cylinder surface whereby it is confined therebetween, means to extract, through said band, stock liquid from the fibrous stock whilst so confined thereby to form a fibrous web, and means adapted to strip the fibrous web from the cylinder surface after passing through the nip or nips of the cylinder and felted press roller or rollers.

Preferably one or more press rollers are provided to press the hand against the cylinder surface.

The accompanying schematic drawing shows, inside elevation, one embodiment of apparatus according to the present invention.

Referring to the drawing, a cylinder 1 is mounted for rotation about a horizontal axis. This cylinder has a surface impervious to liquid, i.e., water, of a paper making stock, which surface may be treated or coated with certain materials to provide desired or appropriate properties of adhesion to a moist fibrous web. Although the surface of the cylinder is impervious in the sense that it will not afford passage of liquid to the interior of the cylinder it may be porous to a shallow depth. Hence the coating applied to the cylinders surface may be porous or non-porous to suit particular requirements. And endless band 2 entrained around a portion of the periphery of the cylinder 1 and is movable therewith. This band 2 is pervious to the liquid of the stock and, for example, may have the same construction as a conventional paper forming wire. The band 2 is entrained around guide rollers 3, any of which, for example the roller indicated at 3', may be movably mounted to adjust the tension of the band. As can be seen in the accompanying drawing, the band 2 and the surface of the cylinder 1 cooperate to form an arcuate nip indicated at 4. An inlet to the nip 4 is shown at 5 and an outlet at 6.

A paper making stock slice 7 discharges into the nip inlet. This slice is in the form of a thin nozzle lying parallel to the axis of the cylinder 1 and extending the full width of the band 2. The opening of the slice is variable and the angle of trajectory of a jet of stock from the slice 7 into the inlet 5 and nip 4 is adjustable.

The guide roller 3" nearest the slice 7 is mounted so as to be movable radially with reference to the cylinder 1 whereby adjustment may be made to its spacing from the cylinder 1, i.e., to the width of the inlet 5. By adjusting the width of the inlet 5 it is possible to produce suction on the outgoing side of said inlet, namely at the start of the nip 4, which suction pulls stock into the nip, giving a shearing effect which helps to disperse the fibres 0f the stock. Also by selectively setting the roller 3" it is possible to create a turbulent pond of stock at the ingoing side of the inlet 4 and this helps to even out irregularities in stock flow thus giving improved web profile. Furthermore, it is possible to obtain a metering action at the inlet 5 whereby the basis weight of the paper web being formed may be controlled and adjusted, The roller 3 usually is solid but it may be cellular or foraminous to alleviate flooding at the nip 4, should this be found to occur.

Three press rolls 10, 11 and 12 bear against the outer exposed surface of the band 2 where it is entrained around the periphery of the cylinder 1 and serve to apply a squeezing action to the fibrous material confined between the band 2 and the surface of the cylinder 1.

It is preferable that the first pressure roll 10 should have a resiliently deformable surface for example, a rubber surface, grooved circumferentially, as shown at 10a, to allow some water to pass through the nip as well as being forced out of the ingoing side of the nip.

After passing through the nip of the first press roll 10, the fibrous material confined between the band 2 and surface of the cylinder 1 is dry enough and strong enough to withstand a light pressure from a plain rubber covered press roll, such as indicated at 11. The third press roller 12 is also a plain rubber covered roller and is applied with fairly heavy pressure without detriment to the fibrous web.

After passing through the nips of the three press rolls 10, 11 and 12, the solids content of the fibrous web has been raised to at least 20% by weight.

Three is not necessarily the optimum number of press rolls that should be used to apply pressure and squeeze the fibrous web whilst it is confined between the band 2 and the surface of the cylinder 1 and more than three rolls may be found optimum when the apparatus is operated at very high speeds. The diameter of the press rolls, the type and hardness of the rubber covering and the nature of the rubber surface, either plain, grooved or drilled, may be varied to suit particular requirements, such as the type of paper or fibrous web being made and the speed at which the apparatus is operated.

In practice it has been found that the band 2 and press rolls 10, 11 and 12 need not necessarily be positively tciiriven but can take their drives from the rotating cylin- Suction boxes may be used in conjunction with or as substitutes for one or more of the press rolls. Such suction boxes would be located in the general are of operation of the rolls 10, 11 and 12, shown in the accompanying drawing.

A liquid collecting pan 13 is disposed below the cylinder 1 to collect and remove stock liquid discharged through the band 2 from the wet fibrous stock confined between the band and the cylinder 1.

At the outlet 6 of the nip 4, the band 2 is entrained away from the surface of the cylinder 1 but the formed fibrous web which may now have a solids content of 20% or more by weight, remains adhering to and in contact with the surface of the cylinder 1.

The adhesion of the fibrous web to the surface of the cylinder 1 must be sufficient to prevent it from being thrown off the surface by said centrifugal force but not so great as to prevent the web from being peeled or stripped from the cylinder surface after it has been further dried to a moisture content of not more than 70%, as will be described. It has been found that unsatisfactory results are obtained if the surface of the cylinder 1 is made of steel. It is possible that a variety of different materials may be used for the cylinder surface and we have found that polytetrafluoroethylene has the required adhesion and release properties. The qualities and properties of the formed fibrous web may be varied and controlled by patterning the surface of the cylinder 1; for example by engraving the cylinder surface with axial grooves, a paper sheet with high stretch characteristics may be produced and by engraving the cylinder surface with circumferential grooves, a paper having physical properties in one direction differing greatly from those in the other direction may be produced.

Two felted presses 20 and 21 bear against the fibrous web after the band 2 has been entrained away and before the fibrous web is stripped from the cylinder 1. These felted presses remove further water, such that when it is finally stripped from the cylinder 1, the moisture content of the web can be made less than 60% which is dryer than a paper sheet presented to the drying cylinders on most conventional paper making machines, and such that the web is self supporting.

The felted press 20 comprises a press roller 22 and an endless felt 23, which is entrained around the roller 22, rolls 24, guide roller 24a and tensioning roller 25. The felt 23 is also passed through the nip of a pair of squeezing press rollers 26.

The felted press 21 likewise comprises a press roller 32, felt 33, rolls 34, guide roller 34a, tensioning roller 35 and squeeze press rollers 36. A smoothing press 40 also bears against the fibrous web adhering to the surface of the cylinder 1 before it is stripped therefrom. As shown in the accompanying drawing this smoothing press is located between the two felted presses 20 and 21.

It is possible to reduce any wire mark that may occur in the Web by pressing the surface of the Web with one or more plain rubber smoothing presses, such as indicated at 40. The smoothing press 40 preferably should not attempt to remove any water from the web and its location, depending upon particular requirements, may be anywhere between the outlet 6 of the nip 4 and the location of stripping the web from the cylinder 1.

As shown in the accompanying drawing, the formed web is stripped from the cylinder 1 after passage through the nip of the second felted press 21 and passed between a pair of cooperating draw felts 51 entrained around driven rollers 52. The felts 51, then, comprise web stripping or removing means in that the felts continue to strip or remove the web 50 from the surface of the cylinder 1.

At initial start-up of the apparatus, the web may be blown off the surface of the cylinder 1 at its location of stripping therefrom and the tail introduced between the draw felts 51 or it is possible to do this manually.

It has been found that the web can be drawn from the surface of the cylinder 1 at various angles but the effect of peeling back at small angle to the normal of the cylinder surface puts minimum stress on the web with very few web breaks. Also at this angle any holes pulled in the web are found to be self-healing and do not cause the web to break. The draw felts 51 are driven at a speed slightly in excess of the peripheral speed of the cylinder 1. An excess speed of the draw felts is necessary due to stretching of the web as it is pulled from the cylinder 1.

The fibrous stock used on the apparatus hereinbefore described may be almost any fibrous slurry normally used for papermaking or any other fibrous slurry found satisfactory. The apparatus may be operated at very high speeds, for example 5,000 ft. per minute, which would be applicable for newsprint but it need not necessarily run at high speed and is suitable for other types of paper. The apparatus has striking versatility in its speed of operation and can be run at only a few feet per minute or at many thousand feet per minute at will. The first few feet of the nip 4 after the inlet 5, is the portion where the fibres of the stock introduced from the slice 7 are formed into a web by the removal of water by a wire or band 2. All the water removed in this vicinity is due to wire tension and centrifugal force. The quality of the formed web is throught to be determined at this initial stage in the process and it can be controlled by a variety of factors such as stock furnish, stock consistency, stock velocity, angle of trajectory of jet, stock drainage rate, stock temperature, wire tension, wire weave and many other variables.

As mentioned hereinbefore, the felts 23 and 33 of the felted presses 20 and 21 are entrained around guide rollers, tension rollers and through the nip of squeezing presses. Further to dry the felts before they are applied to the fibrous web adhering to the surface of the cylinder 1, they may be passed across vacuum boxes but this is thought to be unnecessary if sufficient drying of the felts can be achieved at the squeezing presses.

The provision of small blind holes spaced close together in the surfaces of the press rollers 22 and 32 of the felted presses 20 and 21 assist in removing water from the fibrous web on the cylinder 1. Inside the nip of the felted presses, the fibrous web and the felts are very much compressed by the rollers 22 and 32 and water is squeezed from the web through the felt into the holes in the rollers. At the outgoing sides of the nips of the felted presses, the water in the holes is discharged outwardly into the felts by centrifugal force and is carried away by the felts, or water is thrown off the press rolls 22 and 32 at some location around their surfaces not covered by the felts. The result of the holes in the surfaces of the press rollers 22 and 32 is that excess water which cannot be accommodated in the bodies of the compressed felts is not forced out of the ingoing side of the nips but is carried through the nips.

As mentioned hereinbefore, the moisture content of the web 50 as it is removed from the surface of the cylinder 1 is below 70%, i.e., the solids content is over 30%. A unique feature of the apparatus according to the present invention is that this low moisture content has been achieved without the use of vacuum. Conventional paper making machines use an enormous quantity of vacuum which is power consuming and hence very expensive. Another unique feature of the apparatus according to the present invention is the impossibility of the fibrous web breaking until this low moisture content is achieved.

From the foregoing description it will be appreciated that at no time is the travelling band 2 in contact with a stationary surface or a surface with which there is relative movement. Hence the wear of the band is minimised. This is an important advantage of the present invention over known processing apparatus in which band wear is a problem.

We claim:

1. Apparatus for making a fibrous web, such as paper, in a continuous manner, comprising a cylinder having a liquid impervious surface, rotatable about a horizontal axis, an endless, liquid pervious band entrained around a portion of the cylinder surface and movable therewith, at least one felted press roller adjacent the cylinder surface at a location circumferentially spaced beyond said endless band in the direction of rotation of the cylinder, means for continuously depositing fibrous stock between the band and the cylinder surface whereby it is confined therebetween, means for extracting, through the band, stock liquid from the fibrous stock whilst so confined thereby to form a fibrous web and means for stripping the fibrous web from the cylinder surface after passing through the nip of the cylinder and at least one felted press roller.

2. Apparatus according to claim 1, including at least one press roll means for pressing said band against said cylinder surface.

3. Apparatus according to claim 2, including at least two press rolls, a first of said press rolls being provided with a circumferentially grooved surface of resiliently deformable material.

4. Apparatus for making a fibrous web such as paper in a continuous manner comprising a cylinder having a liquid impervious surface, rotatable about a horizontal axis, an endless liquid pervious band entrained around a portion of said cylinder surface and movable therewith, at least two felted press rollers adjacent said cylinder surface at locations circumferentially spaced beyond said endless band in the direction of rotation of the cylinder, slice means for continuously depositing fibrous stock between said band and said cylinder surface, whereby said stock is confined therebetween, means for extracting stock liquid through the band from the fibrous stock whilst so confined, thereby to form a fibrous Web, and a pair of draw felts located beyond said felted press rollers for sandwiching said fibrous web and pulling said web back from said cylinder surface at an acute angle with respect to the normal of said surface.

5. Apparatus for making a web of paper or the like comprising a rotatable cylinder having a liquid impervious surface, a movable liquid pervious band entrained adjacent a portion of said cylinder surface for movement therewith, slice means for depositing fibrous stock between said band and said cylinder surface, means for removing stock liquid from the stock through said liquid pervious band to form a fibrous web from said stock, at least one felted press roller adjacent said cylinder surface at a location removed from said band in the direction of rotation of said cylinder for sandwiching the fibrous web between said cylinder surface and said felted press roller, and means for removing the fibrous web from said cylinder surface subsequent to the passage of the fibrous web between said cylinder surface and said felted press roller.

References Cited UNITED STATES PATENTS 3,056,719 10/1962 Webster 1623 18 3,201,305 8/1965 Webster 162-3 18 3,236,724- 2/1966 Wahlstrom 1623 17 FOREIGN PATENTS 614,901 2/1961 Canada.

S. LEON BASHORE, Primary Examiner.

R. BAJEFSKY, Assistant Examiner. 

1. APPARATUS FOR MAKING A FIBROUS WEB, SUCH AS PAPER, IN A CONTINUOUS MANNER, COMPRISING A CYLINDER HAVING A LIQUID IMPERVIOUS SURFACE, ROTATABLE ABOUT A HORIZONTAL AXIS, AN ENDLESS, LIQUID PERVIOUS BAND ENTRAINED AROUND A PORTION OF THE CYLINDER SURFACE AND MOVABLE THEREWITH, AT LEAST ONE FELTED PRESS ROLLER ADJACENT THE CYLINDER SURFACE AT A LOCATION CIRCUMFERENTIALLY SPACED BEYOND SAID ENDLESS BAND IN THE DIRCTION OR ROTATION OF THE CYLINDER, MEANS FOR CONTINUOUSLY DEPOSITING FIBROUS STOCK BETWEEN THE BAND AND THE CYLINDER SURFACE WHEREBY IT IS CONFINED THEREBETWEEN, MEANS FOR EXTRACTING, THROUGH THE BAND, STOCK LIQUID FROM THE FIBROUS STOCK WHILST SO CONFINED THEREBY TO FORM A FIBROUS WEB AND MEANS FOR STRIPPING THE FIBROUS WEB FROM THE CYLINDER SURFACE AFTER PASSING THROUGH THE NIP OF THE CYLINDER AND AT LEAST ONE FELTED PRESS ROLLER. 